U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska


Date of this Version


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Agricultural Research March 2013.


Americans everywhere are struggling to lose weight—and to keep from putting those lost pounds right back on. For many, it’s discouraging to have their best efforts fail while those of other dieters succeed.

Researchers at the Agricultural Research Service’s Western Human Nutrition Research Center in Davis, California, are conducting studies that may provide new insights into the underlying causes of this disparity in dieting success.

Given America’s obesity epidemic, such research is timely and relevant. The U.S. Centers for Disease Control and Prevention estimates that 35 percent of U.S. adults and 18 percent of kids and adolescents age 6 through 19 are overweight or obese. Both conditions are associated with increased risk of type 2 diabetes, cardiovascular disease, and other chronic disorders.

Chemist Nancy L. Keim, nutrition scientist Kevin D. Laugero, and their colleagues have looked at several factors that may affect weight-management success. Their analysis included assessing volunteers’ patterns of decisionmaking and evaluating changes in their levels of cortisol—a stress-associated hormone.

The study volunteers, 29 obese but otherwise healthy women age 20 to 45, were asked to eat all their meals at the nutrition center, where their food was prepared for them. The research began with a 3-week baseline phase, during which the intent was to stabilize the volunteers’ weight. That was followed by a 12-week reduced-calorie regimen intended to help the volunteers shed pounds. During this weight-loss phase, meals provided 500 fewer daily calories than the total each volunteer would have needed if the goal had been to maintain her weight.